室溫操作之砷化銦量子點光子晶體雷射

Abstract

我們在砷化鎵基板上成功製作單層砷化銦量子點的光子晶體奈米共振腔，在製程方面，藉由電子束直寫微影技術，以及經由乾式蝕刻與濕式蝕刻的步驟，將光子晶體奈米共振腔製作出來。並在室溫利用連續波雷射激發出雷射光，在300K的臨界激發強度為11.6 μW。 我們設計以線缺陷L3系列為主的共振腔，藉由改變特徵尺寸，我們發現共振模態會紅移，與預期理論吻合。並利用兩側相鄰孔洞半徑減小和位移，以期製作出高品質係數和低臨界激發強度的微共振腔。 我們使用微光激發螢光系統在不同溫度做量測，在80K溫度下，最低量測到的臨界激發強度為217 nW，接著我們做變溫量測，在室溫300K仍然可以清楚觀察到共振腔模態，臨界激發強度為11.6 μW。而由於不同溫度下，共振腔的有效折射率會產生變化，導致模態紅移，紅移量為0.054 nm/K。在不同的激發強度下，模態的紅移量因光子晶體散熱不佳的因素，在高溫特別明顯。

We have successfully fabricated photonic crystal slab nanocavities on a GaAs substrate with a single layer of InAs quantum dots as active medium. The photonic crystal nanocavities were fabricatedby E-beam lithography, dry etching, and wet etching. Lasing can be observed in continuous wave operation at room temperature, and the threshold pump power is 11.6 μW. We designed a point defect structure, called L3 defect, which consists of three missing air holes along one direction. We observed the resonant mode has red shift with different r/a ratios. The two nearby holes were shrunk and shifted in the one direction to produce a nanocavity with a higher quality factor and lower threshold power. We performed the micro-photoluminescence measurements on the fabricated devices at different temperatures. The lowest threshold power we observed at 80 K is 217 nW. The cavity mode can still be observed clearly at room temperature with the threshold power of 11.6 μW. Because the effective refractive index of the resonant cavities changes with temperature, the mode shows red shift of 0.054 nm/K. Due to the heat dissipation issue in photonic crystal cavities, higher red shifts are observed for higher pumping, especially at higher operating temperature.